The present invention relates generally to foundry molding and more particularly to a method and apparatus for the removal of sand bales containing castings from molding boxes of poured foundry molds.
In order to better utilize their molding surfaces, foundry molds which are made of clay-bonded molding sand are usually compacted in molding boxes and they are poured in the form of upper and lower halves combined to form a complete foundry mold. The use of such molding boxes becomes inevitable when the foundry mold exceeds a certain size. Since high-pressure compacting of foundry molds is utilized with greater frequency, and since, as a result, the forces acting on the inner surfaces of the molding boxes during compacting of the molding sand become larger, the molding boxes must be made with a stiffer construction. As a result, the cost of the molding boxes is increased.
The physical values or characteristics of finished castings will usually depend on the cooling time. Furthermore, it is usually required that castings have a residual stress which is as small as possible after cooling. Accordingly, it is desirable that castings cool slowly after pouring, sometimes for up to one hour or more while remaining in the molding sand.
The aforementioned requirements tend to cause an increase in the costs incurred for the molding boxes not only in respect to the plant involved but also with regard to the costs of operation, and this is no longer economically acceptable. Therefore, devices are known in which the sand bales containing the castings are removed from the molding boxes as soon as the castings have a temperature which is safely below the eutectoid temperature.
Such known devices for removing sand bales from the molding boxes may comprise a punch or die which interacts with a support, wherein the molding boxes rest on the support and the punch pushes the sand bales out of the molding halves. However, these devices have the disadvantage that very high forces of the die are required to remove the sand bales. Aside from the cumbersome construction which is required for applying these forces, such die forces also give rise to the danger that the castings which are sensitive to deformation may be damaged.
According, it is the intent of the present invention to provide means for the separation from the molding boxes of the sand bales within which the castings are contained while avoiding forces which may deform the sand bales.